Screening polyembryonic mango accessions for salt tolerance and assessing dynamics of sodium (Na+), potassium (K+), and antioxidants

Introduction - Salinity is an important abiotic stress limiting mango production worldwide. Salt tolerant polyembryonic rootstock enables mango cultivation in salt-affected and wastelands. The objective of the study was to assess the field tolerance of polyembryonic mango accessions in salt affected sodic soils, through the dynamics of sodium, potassium, antioxidants and associated biochemicals in response to salt stress. Materials and methods - The rootstocks were collected from seawater inundated zone of the South Andaman Islands and then evaluated at the experimental farm of ICAR-Central Soil Salinity Research Institute, Lucknow, India for a period of two years (2014-2016). The variables plant height, survivability percentage, Na+/K+ ratio, phenol and proline contents, superoxide dismutase (SOD) and peroxidase (POD) activities were assessed. Results and discussion - Among the accessions, 'NIL-2' and 'ML-6' showed higher tolerance to salt stress with complete survival (100%). Similarly, the data on plant height were significantly similar to those of the control '131'. The data of Na+/K+ ratio in leaves and meristem tips indicated an effective Na+ exclusion mechanism adopted by 'ML-2' and 'ML-16' through increased uptake in K+. Increased accumulation of proline and phenolics in 'ML-2' and `ML-6' with the increase in the activities of SOD and POD led them to a better survivability in salt stress conditions. Conclusion - Our investigation has led to the selection of two salt stress tolerant rootstocks (cvs. 26 ML-2 and ML-6) suitable for mango production in salt affected sodic soils in tropical and sub-tropical conditions.